1. Field of the Invention
The present invention relates to a light intensity controller for a color image forming apparatus, and more particularly to an image forming apparatus for making a color copy by forming electrostatic latent images based on color images of an original produced by color decomposition.
2. Description of the Prior Art
In a prior art copying machine having a variable magnification ratio copy function, in order to compensate for the change in a light intensity per unit area for different magnification ratios, a magnification of an optical system is changed in accordance with the magnification ratio and an effective voltage to a light exposure lamp (halogen lamp) is changed in accordance with the magnification to adjust the light intensity.
However, it has been known that when the effective voltage to the halogen lamp is changed, not only a color temperature, a current and a light emitting efficiency of the lamp change but also a peak wavelength shifts to a red region and hence an energy distribution also shifts. Accordingly, when the light intensity is adjusted simply in accordance with the magnification ratio, a color balance of the color copying machine is lost.